This invention relates to a mechanism for use with a packaging machine for sealing the tops of flexible pouches as the pouches are advanced at high speed and with continuous motion along a predetermined path. Such a sealing mechanism includes a plurality of sealing heads which track the moving pouches, each of the heads having a pair of heated bars which seal the pouch.
A packaging machine with a continuous motion top sealing mechanism is disclosed in Nutting et al U.S. Pat. No. 3,230,687. That sealing mechanism, however, is complex and expensive and requires a considerable amount of floor space in the lengthwise direction of the machine. In addition, each of the sealing heads of the Nutting et al mechanism has sealing bars which move in separate orbital paths and thus it is difficult to maintain precise control over the bars and particularly with respect to the sealing pressure which is exerted by the bars.
The invention has more particular reference to a top sealing mechanism for a packaging machine in which steam is introduced into the pouches just prior to the time the pouches are sealed. A packaging machine in which the pouches are flushed with steam is disclosed in Johnson U.S. Pat. No. 4,081,942. The Johnson machine, however, operates with intermittent motion rather than with continuous motion and thus the pouches dwell while their tops are being sealed.